1. Field of the Invention
The present invention relates generally to a display device, and in particular to an organic light emitting display (OLED) having a structure to improve display quality.
2. Description of Related Art
An organic light emitting display (OLED) is self-emissive and generally includes a plurality of pixels. Each pixel includes an anode, an organic light emitting layer, and a cathode. The organic light emitting layer includes an organic material having a low molecular weight or polymer. When a voltage is applied to the pixel, a positive charge from the anode is combined with a negative charge from the cathode to form excitons in the organic light emitting layer, and light is generated from the organic light emitting layer when holes are combined with electrons moving to a lower energy state.
Conventionally, a partition member is formed on the anode to cover edges of the anodes while exposing a portion of the anode via an aperture. Typically, the aperture has been a rectangular shape and the corners of the aperture have had right angles. The organic light emitting layer is formed by an ink jet method, in which an ink jet dispenses organic material through each aperture. The partition member holds the organic material in a specific pixel area and prevents organic material from diffusing to other pixels.
Organic material has a liquid phase which has the property of keeping surface tension energy as low as possible. Therefore, when organic material is dispensed onto the anode through the aperture, the organic material forms into a spherical shape to keep the surface tension energy low. Disadvantageously, organic material cannot fill (or wet) sharp corners (e.g., at right or acute angles) of the aperture exposing the anode. If the corners of the aperture are not completely filled (or wetted) with organic material, the organic light emitting layer does not have uniform thickness. Lack of thickness uniformity causes the brightness of the display (i.e., display luminance) to lack uniformity. Also, the anode and cathode may contact and cause a short circuit in the area where organic material cannot fill completely.
Accordingly, a display device with improved uniformity in the organic light emitting layer and a fabrication method thereof are highly desirable.